Circuit pattern forming method and circuit pattern forming device
The present invention provides a circuit pattern forming device and a circuit pattern forming method both of which can eliminate problems, such as open circuits and short circuits, when forming circuit patterns on the substrate and which can form circuit patterns of a thin film uniform in thickness. To this end, the present invention forms liquid dots on the substrate with gaps between the dots. Then, it further forms liquid dots between the liquid dots, thus forming a liquid circuit pattern. The circuit pattern is then solidified by a fixing step.
Latest CANNON KABUSHIKI KAISHA Patents:
- IMAGE PROCESSING APPARATUS, IMAGE PROCESSING METHOD, AND PROGRAM
- Image processing apparatus and image processing method
- ELECTROPHOTOGRAPHIC PHOTOSENSITIVE MEMBER, PROCESS CARTRIDGE, ELECTROPHOTOGRAPHIC APPARATUS AND PHTHALOCYANINE CRYSTAL
- Method, apparatus and system for generating intra-predicted samples
- OSCILLATOR
1. Field of the Invention
The present invention relates to a circuit pattern forming method and a circuit pattern forming device to form circuit patterns on circuit boards used in electronic devices, electric devices, computers and communication devices, and more particularly to a circuit pattern forming method and a circuit pattern forming device that form circuits by ejecting a circuit pattern forming solution onto a substrate.
-
- 2. Description of the Related Art
Printed circuit boards installed in electronic devices, communication devices and computers are mounted with a variety of kinds of semiconductor devices, such as LSIs, and of electronic components. Many kinds of printed circuit boards are available, including those using ceramics as a base material, those using as a base material a composite material formed of a reinforcement material such as glass fibers and a synthetic resin such as epoxy resin, and those using a flexible film, such as polyester resin and aramid resin, as the base material. Most of the conventional printed circuit boards have used a one-sided or double-sided substrate. As electronic devices have been miniaturized and packed in higher density, laminated circuit patterns have come to be used. At present eight- or 16-layer printed circuit boards are becoming a mainstream. At the same time, circuit patterns are also being formed of increasingly finer circuits and their density rapidly increasing.
Japanese Patent Application Laid-open No. 07-245467 (1995) discloses a method of forming circuits by directly ejecting a conductive solution and an insulating solution onto a surface of a substrate by an ink jet method to draw conductive patterns and insulating patterns. This method obviates a subtractive method, which in turn offers an advantage of being able to reduce the number of steps required and eliminate the need to process a waste liquid produced during plating and etching steps.
In the Japanese Patent Application Laid-open No. 07-245467 (1995), circuit patterns are formed by ejecting ink droplets from an ink jet printer such that adjoining droplets on a substrate overlap each other. This is because, if the adjoining droplets fail to overlap, those portions that are out of contact with each other will lead to an open circuit. With this method, however, droplets ejected onto the substrate contact and merge with the existing droplets on the substrate and may form liquid puddles.
Let us explain about the liquid puddles thus formed.
Under these circumstances, proposals have been made to prevent forming of such liquid puddles and therefore the problems of open-circuits and short-circuits, as disclosed in Japanese Patent Application Laid-open No. 2003-133691. This method, as shown in
Then, the printed substrate is subjected to a drying step to fix the dots 1006 formed by the first ejection step. After this, a second ejection step is performed to form dots 1007. In forming the dots 1007, droplets 1003 are ejected to positions different from those of the first ejection step at the same pitch 1005 as the first ejection step. Then, the substrate is dried again to fix the dots 1007 formed in the second ejection step. After this, dots 1008 are formed in a third ejection step. In forming the dots 1008, droplets 1003 are ejected at a smaller pitch than the pitch 1005 of,the first ejection step.
As described above, in Japanese Patent Application Laid-open No. 2003-133691, dots are formed on the substrate at intervals and then dried, after which droplets are ejected between the formed dots. With this arrangement, the landing droplets are not attracted to the existing dots on the substrate, preventing the formation of liquid puddles. Further, Japanese Patent Application Laid-open No. 2003-133691, as shown in
An object of this invention is to provide a circuit pattern forming device and a circuit pattern forming method, both of which can eliminate problems, such as open circuits and short circuits, when forming a circuit pattern on a substrate and which can form a circuit pattern of a thin film uniform in thickness.
To achieve the above objective, the present invention has the following construction.
According to a first aspect, the present invention provides a circuit pattern forming method which comprises: a first ejection step of ejecting a circuit pattern forming liquid onto a substrate by using a liquid ejection means to form dots of the liquid on the substrate with gaps between them; a second ejection step of ejecting the liquid from the liquid ejection means to further form dots of the liquid between the dots of the liquid on the substrate, thereby forming a liquid circuit pattern; and a fixing step of solidifying the liquid circuit pattern.
According to a second aspect, the present invention provides a circuit pattern forming device to form a circuit pattern by ejecting a circuit pattern forming liquid onto a substrate from a liquid ejection means to form a plurality of dots of the liquid on the substrate, the circuit pattern forming device comprising: a moving means to move the liquid ejection means relative to the substrate; a detection means to detect a position of the liquid ejection means with respect to the substrate; and a control means to, based on the position of the liquid ejection means with respect to the substrate as detected by the detection means and on circuit pattern forming data, form dots of the liquid on the substrate with gaps between the dots and then further form dots of the liquid on the substrate between the dots of the liquid on the substrate, thereby forming a liquid circuit pattern.
With this invention, a flat, thin film with an almost uniform thickness can easily be formed on the substrate by ejecting droplets onto the substrate with gaps between the dots and then further ejecting droplets to the gaps between those dots that need to be connected, before the previously formed dots on the substrate solidify. Therefore, this invention can alleviate the problem of open circuits and short circuits and undesired conduction and can also meet requirements for higher density and multilayer construction demanded by circuit boards of recent years.
The above and other objects, effects, features and advantages of the present invention will become apparent from the following description of embodiments thereof taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Now, embodiments of this invention will be described in the following order.
-
- 1. Construction of Circuit Pattern Forming Device
- 2. Configuration of Control System
- 3. Control of Circuit Forming Position
- 4. Material Used in Circuit Pattern Forming Process
- 4-1. Substrate
- 4-2. Conductive Solution and Insulating Solution
- 5. Circuit Pattern Forming Process
[1. Construction of Circuit Pattern Forming Device]
As one embodiment of this invention, a circuit pattern forming device used to form a circuit pattern made up of an insulating pattern and a conductive pattern on a substrate will be described.
The circuit pattern forming device used in this embodiment of
In
The carriage 109 reciprocally moves in the main scan direction (X direction) along an upper surface of the bed, i.e., a stage surface. The CR linear motor 101 and the LF linear motor 102 each incorporate a linear encoder 111, 112 and an origin sensor 106, 107. The outputs of the linear encoder 111, 112 and the origin sensor 106, 107 are used as a servo control input for driving the linear motors. Further, the linear encoder 111 on the carriage side is used to generate a solution ejection timing.
Further, the circuit pattern forming device of this embodiment is connected with a personal computer (not shown) as a host device. Based on figure information (circuit pattern forming information) sent from this personal computer, the circuit pattern forming device moves the liquid ejection heads 2, 3, ejects solutions and moves the stage 103 to form a circuit pattern on the surface of the substrate 1.
A heater (not shown) is embedded in a lower part of the stage 103 on which the substrate 1 is mounted. The heater heats the circuit pattern drawn on the substrate to fix it. In this embodiment since the heater is intended to fix the circuit pattern, its heating temperature is set to 40-70° C., enough to fix the liquid on the substrate 1 even in this simple construction. With the fixing complete, no functional problem will arise in the circuit board. However, for an improved conductivity of the conductive pattern and an improved insulation performance of the insulating pattern, the circuit board may be burned in a separate baking device.
[2. Configuration of Control System]
Next, the control system for the circuit pattern forming device in this embodiment will be described.
A main control unit 44 is a central part of the control system that controls the entire circuit pattern forming device of this embodiment including the liquid ejection head and the mechanical unit 46. The main control unit 44 has a CPU, a ROM in which operation programs are stored, and a work RAM that allows reading and writing of a variety of data.
The main control unit 44 outputs a control signal to the mechanical unit 46 to perform a mechanical control, for example, on the movement of the carriage 109 and stage 103. It also transfers signals to and from a head control unit 42, a memory control unit 50 and a drawing position signal generation unit 41 to control the operation of the liquid ejection head 2. An I/F unit 47 is an interface between the personal computer not shown and the circuit pattern forming device. The I/F unit 47 receives a command and circuit pattern drawing data (circuit pattern data) from the host (personal computer). The memory control unit 50 transfers the command from the I/F unit 47 to the main control unit 44 and, under the control of the main control unit 44, generates an address signal and a write timing signal to write the circuit pattern drawing data into a buffer memory 45.
Further, the main control unit 44 analyzes the command received from the I/F unit 47 and, according to the result of the analysis, sets drawing conditions, such as a drawing speed and a drawing resolution. Then, based on the drawing conditions, the main control unit 44 controls the mechanical unit 46 and the drawing position signal generation unit 41 to execute the drawing operation under the predetermined conditions.
Further, the circuit pattern drawing data received from the personal computer not shown is stored in the buffer memory 45 or a temporary memory and then transferred to the head control unit 42 by the control of the memory control unit 50 that has received the command from the main control unit 44.
In synchronism with the drawing position signal output from the drawing position signal generation unit 41, the head control unit 42 drives individual nozzles of the liquid ejection head to draw a circuit pattern according to the circuit pattern drawing data transferred from the buffer memory 45.
[3. Control of Circuit Forming Position]
Next, the drawing position control method in the circuit pattern forming device of this embodiment will be described.
By counting the output signal from the linear encoder 111, as described above, the mobility position of the moving carriage 109 can be determined. That is, a position detector 40 in
Similarly, a circuit made up of components 205-208 of
In
The origin signal Z, the count signal PLS and the travel direction signal DIR are connected to input terminals of the up/down counter 210—reset (CLR), clock (CK) and up/down (UP/DW). Thus, when the carriage 109 moves to the origin position (home position) in response to an initialize command from the main control unit 44, the origin signal Z becomes active, clearing the count value to zero (count value=0). From this time on, with the count value=0 taken as an origin, the absolute position of the carriage 109 in the main scan direction is counted and the count value is output to the drawing position signal generation unit 41.
When writing data from the main control unit 44 into the RAM 300, the selector 301 is switched to the CPU side. During the drawing operation, the selector 301 is switched so that the count value is supplied to the address input of the RAM 300. As the carriage 109 travels, the RAM data of address representing the position of the carriage 109 is output to the head control unit 42.
With the drawing data written into RAM 300 in advance from the CPU of the main control unit 44, a drawing position pulse is output to the head control unit 42 each time the carriage 109 reaches the drawing position. Upon receiving the drawing position pulse, the head control unit 42 drives the liquid ejection head 2 to eject a solution to the substrate 1.
In
The forward direction pulse and the backward direction pulse shown in
In
While in
[4. Material Used in Circuit Pattern Forming Process]
[4-1. Substrate]
The substrate 1 used in this invention is shaped planar in the form of film, sheet and plate. Because forming a circuit pattern layer includes a baking step, the substrate preferably has high heat resistance. A substrate with a curved surface, rather than a planar surface, may be used if it can be formed with circuit patterns by the ink jet system. The substrate may use the following materials: ceramics which are made to sinter alumina-silica, thermoplastic resin films, such as polyester film, aromatic polyamide film and polyimide film; cloths and nonwoven fabric of glass fibers, polyester fibers and aromatic polyamide fibers impregnated with thermoplastic resin and epoxy resin and then hardened and shaped like a sheet; a glass epoxy laminated plate used for ordinary circuit boards; and permeable substrate, paper and cloth. It is desired that the substrate used in this invention have a hydrophilic property. It is particularly preferred that the substrate be surface-treated so that the solution that has landed on the substrate has a surface tension enough to prevent it from spreading and wetting the substrate surface. Even those substrates with water repellency may be used as long as they are given the similar surface treatment.
[4-2. Conductive Solution and Insulating Solution]
Now, the conductive solution and insulating solution used in this embodiment will be explained.
The conductive solution used in this embodiment includes water and a conductive material. Water used to prepare the conductive solution is preferably industrial water removed of cations and anions by a deionization process. The amount of water in the conductive solution is determined in a wide rage according to a water percentage required or characteristics required of the conductive solution. Generally, the water content falls in a range of 10-98 weight percentage and preferably in a range of 40-90 weight percentage.
A conductive material used in the conductive solution is, for example, metal superfine particles less than 1-100 nm in average diameter that are manufactured by laser abrasion. The metal superfine particles may include, for example, ITO (indium-tin oxide) and SnO2 (tin oxide).
The insulating solution used in this invention contains water, an insulating material and a second component. The second component is an alkaline water solution which, when it comes into contact with the conductive material used in the conductive solution, causes an interface coagulation at a contact area by a coagulation sedimentation reaction based on a pH difference, preventing a mixing or bleeding of the conductive solution and the insulating solution, keeping these solutions isolated from each other. This alkaline water solution evaporates during thermosetting processing performed as post processing. The water used in the insulating solution may be the one used in the conductive solution.
A material that may be used as the second component includes any kinds of polymer, such as an anionic water-soluble polymer and a volatile amine. The anionic water-soluble polymer as the second component may include ammonium salt and the volatile amine may include ammonium hydroxide. As the insulating material a nonionic polymer may be used. An example of the nonionic polymer includes a solder resist containing epoxy resin as the main component.
[5. Circuit Pattern Forming Process]
First Embodiment
First, let us explain about a first ejection step.
As shown in
Next, a second ejection step will be explained.
After the large liquid dots 12 are formed on the substrate 1 by the first ejection step, the head 2 is immediately returned to the drawing start position (left end of the substrate 1). Then, as the head 2 is moved again in the forward direction, large droplets 10 of the insulating solution are ejected between the existing, adjoining large dots 12, 12 on the substrate 1, as shown in
In this second ejection step, because two large dots 12 and a large droplet 10 need to contact each other, the diameter D of the large droplet 10 must be larger than the gap 17 between the two large dots formed on the substrate, as shown in
While
The definition of the gap used in this specification will be described.
Though not shown, the forming of the insulating pattern and the conductive pattern on the second and subsequent layer can be performed in a manner similar to that used for the first layer pattern.
Second EmbodimentNext, a second embodiment of this invention will be explained.
In the second embodiment, the insulating pattern and the conductive pattern are formed simultaneously.
Let us first explain about a first ejection step.
As shown in
Next, as shown in
Next, a second ejection step will be described.
After large liquid dots 12a, 12b have been formed on the substrate 1 by the first ejection step, the liquid ejection heads 2, 3 are immediately returned to the drawing start position (left end of the substrate 1). Then, before the large dots 12a, 12b on the substrate 1 turn from liquid into a gel state, a large droplet 10a of the conductive solution is ejected onto the gap 17a between the dots 12a, 12a that were formed on the substrate 1 in the first ejection step, as shown in
At this time, since the large dots 12a, 12b formed in the first ejection step have not yet gelled, when the large droplet 10a comes into contact with the large dots 12a, they attract each other and mix, as shown in
Although an example case in which a single layer circuit board is fabricated has been described by referring to
Further, in a pattern forming method using materials that can be ejected in a liquid state, a wide range of materials, including conductive patterns, insulating patterns and semiconductive materials, can of course be applied.
First, in forming a first layer, the insulating solution and the conductive solution are used and large droplets are ejected to a gap between large dots as in the first and second ejection step to form patterns of a thin film almost uniform in thickness, as shown in
Next, a second layer is formed over the first layer. This involves, as shown in
A third layer is made by performing the pattern forming as with the first and second layer (see FIG. 13E). The pattern is then heat-treated to fix the third layer, as shown in
Next, a third embodiment of this invention will be described.
If the solutions used (insulating solution and conductive solution) have a characteristic that they turn from a liquid to a gel in a short period of time, the third embodiment makes it possible for large dots formed in the first ejection step and large droplets ejected in the second ejection step to mix, by shortening a process time taken from the first ejection step to the second ejection step. As shown in
By referring to
When an insulating solution with a long fixing time (the time it takes for the ejected droplets to change its state from liquid to gel) is used, the liquid ejection head needs to be moved to the drawing start position (left end of the substrate 1) before initiating the second ejection step, as in the first and second embodiment. If, however, this method is applied to a solution with a short fixing time characteristic, large dots ejected in the first ejection step may solidify during a period from the first ejection step to the second ejection step, resulting in the droplets ejected in the two ejection steps failing to mix together. To deal with this problem, the third embodiment executes the first ejection step and the second ejection step in one and the same scan of the head 4 so as to eject droplets in the second ejection step before the dots formed in the first ejection step solidify.
That is, as shown in
Next, after a large dot 12B of the insulating solution has been formed on the substrate 1, the nozzle array 30c situated directly behind in the scan direction ejects a large droplet of the insulating solution from a nozzle 20 (see
Next, a fourth embodiment of this invention will be explained.
As shown in
For this purpose, the fourth embodiment uses a liquid ejection head 5 shown in
By referring to
The method of changing the size of droplets used in the first ejection step and the second ejection step, as the fourth embodiment of this invention, will be explained. In the fourth embodiment, too, the insulating solution is used as an example. The similar method can also be applied for the conductive solution.
First, as shown in
Next, the second ejection step will be explained.
In the fourth embodiment, too, the second ejection step is initiated without moving the head 5 to the drawing start position (left end of the substrate 1), as in the case with the third embodiment. That is, as shown in
As described above, in the fourth embodiment, the droplet ejected in the second ejection step is reduced in size according to a narrow gap 17 between the large dots 12A, 12B formed in the first ejection step, so the merge of the droplet with the large dots prevents the droplet from spreading outwardly, assuring a more precise forming of circuit patterns.
The present invention has been described in detail with respect to preferred embodiments, and it will now be apparent from the foregoing to those skilled in the art that changes and modifications may be made without departing from the invention in its broader aspect, and it is the intention, therefore, in the appended claims to cover all such changes and modifications as fall within the true spirit of the invention.
This application claims priority from Japanese Patent Application No. 2005-181622 filed Jun. 22, 2005, which is hereby incorporated by reference herein.
Claims
1. A circuit pattern forming method comprising:
- a first ejection step of ejecting a circuit pattern forming liquid onto a substrate by using liquid ejection means to form dots of the liquid on the substrate with gaps between the dots;
- second ejection step of ejecting the liquid from the liquid ejection means to further form dots of the liquid between the dots of the liquid on the substrate, thereby forming a liquid circuit pattern; and
- a fixing step of solidifying the liquid circuit pattern.
2. A circuit pattern forming method according to claim 1, wherein the first ejection step, the second ejection step and the fixing step are repetitively performed on the circuit pattern formed on the substrate to form a circuit pattern of a laminated layer structure.
3. A circuit pattern forming method according to claim 1, wherein a diameter of droplets ejected in the second ejection step is larger than the gap between the dots formed on the substrate in the first ejection step that need to be connected.
4. A circuit pattern forming method according to claim 1, wherein the circuit pattern forming liquid includes a conductive solution containing conductive particles to form a conductive pattern and an insulating solution to form an insulating pattern.
5. A circuit pattern forming device to form a circuit pattern by ejecting a circuit pattern forming liquid onto a substrate from a liquid ejection means to form a plurality of dots of the liquid on the substrate, the circuit pattern forming device comprising:
- moving means for moving the liquid ejection means relative to the substrate;
- detection means for detecting a relative position of the liquid ejection means with respect to the substrate; and
- control means for, based on the position of the liquid ejection means and the substrate detected by the detection means and on circuit pattern forming data, forming the dots of the liquid on the substrate with gaps between the dots and then further form dots of the liquid on the substrate between the dots of the liquid on the substrate, thereby forming a liquid circuit pattern.
6. A circuit pattern forming device according to claim 5, wherein the liquid ejection means ejects the liquid as it scans relative to the substrate, and
- the control means performs control such that a direction in which the liquid ejection means scans to form the dots of the liquid on the substrate with gaps between the dots is equal to a direction in which the liquid ejection means scans to eject droplets from the liquid ejection means to fill the gaps between the dots of the liquid that need to be connected.
7. A circuit pattern forming device according to claim 5, wherein the liquid ejection means ejects the liquid as it scans forwardly and backwardly relative to the substrate, and
- the control means performs control such that the scan of the liquid ejection means to form the dots of the liquid on the substrate with gaps between the dots and the scan of the liquid ejection means to eject droplets to fill the gaps between the dots of the liquid that need to be connected are performed in both forward and backward directions.
8. A circuit pattern forming device according to claim 6, wherein the liquid ejection means has a plurality of nozzle arrays arranged side by side in the scan direction, each nozzle arrays having a plurality of liquid ejection nozzles arrayed in a direction crossing the scan direction, and
- the scan of the liquid ejection means to form the dots of the liquid on the substrate with gaps between the dots and the scan of the liquid ejection means to eject droplets to fill the gaps between the dots of the liquid that need to be connected are the same scan.
9. A circuit pattern forming device according to claim 8, wherein the nozzle arrays have a large nozzle array made up of large nozzles for ejecting large droplets and a small nozzle array made up of small nozzles for ejecting droplets of smaller diameter than that of the large droplets,
- wherein the control means causes the large nozzles to eject large droplets onto the substrate to form large liquid dots with gaps between the dots and causes the small nozzles to eject small droplets to fill the gaps between the large dots that need to be connected.
Type: Application
Filed: Jun 19, 2006
Publication Date: Dec 28, 2006
Patent Grant number: 7867561
Applicant: CANNON KABUSHIKI KAISHA (Tokyo)
Inventors: Takashi Mori (Tokyo), Yuji Tsuruoka (Kawasaki-shi), Masao Furukawa (Yokohama-shi), Seiichi Kamiya (Yokohama-shi), Nobuhito Yamaguchi (Tokyo)
Application Number: 11/454,862
International Classification: B41J 29/393 (20060101);